The formation of free radicals is a widely accepted pivotal mechanism leading to skin aging. Free radicals are highly reactive molecules with unpaired electrons that can directly damage various cellular membranes, lipids, proteins, RNA and DNA. The damaging effects of these reactive oxygen species are induced internally during normal metabolism and externally through various oxidative stresses. UV exposure and environmental pollution can accelerate skin aging by producing free radicals in skin. Antioxidants protect cells from the damage of oxidative stress by scavenging free radicals and inhibiting following oxidation reactions. The topical application of antioxidants is broadly used in skin care products to prevent skin aging.
Mangiferin, a C-glucoside of tetrahydroxy-1,3,6,7 xanthone, is known to be an effective anti-microbial and anti-oxidant in which these activities are optimal below pH 5, and are diminished at pH that is greater than 7. In addition, the solubility of mangiferin in water and other common solvents for cosmetic applications is known to be adversely affected at lower temperatures (e.g., at 4° C.), and at pH that is less than 7. Hydrotropes such as niacinamide and caffeine have been used to enhance the solubility of mangiferin, but inclusion of hydrotropes does not provide any benefit with respect to its chemical stability, particularly in compositions having low pH (2-3), and in some compositions the level of hydrotrope needed for suitable solubility can have unwanted effects on the composition.
For the foregoing reasons, it is an object of the present invention to provide compositions in which mangiferin solubility and activity is preserved independent of temperature and pH.